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Avalanche Forecast

Archived

Dec 16th, 2018–Dec 17th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Inland.

We're lacking information about how reactive the new snow has been, so it's critical to make your own observations. Back off if you see recent avalanches, cracking, or whumpfing.

Confidence

Low - Due to the number of field observations

Weather Forecast

SUNDAY NIGHT: Cloudy with isolated flurries, strong wind from the southwest, alpine temperatures around -4 C.MONDAY: Cloudy with scattered flurries and localized accumulations of 5 cm by the afternoon, strong wind out of the southwest, alpine high temperatures around -3 C.TUESDAY: 5-15 cm of snow, strong wind out of the southwest, alpine high temperatures around -3 C.WEDNESDAY: Mostly cloudy with isolated flurries, moderate to strong wind from the southwest, freezing level drops with alpine high temperatures around -5 C.

Avalanche Summary

No recent avalanches have been reported, but several natural slab avalanches were reported during the start of the stormy weather last week. Two large (size 2) avalanches were observed on east-facing wind-loaded slopes near treeline (1700 m) and several smaller slabs have been reported in steep gullies at lower elevations. See this MIN report. These avalanches likely failed on the interface between the storm snow and old snow that is now roughly 40-70 cm below the surface. This slab produced notable cracking with skier traffic last week and could produce large human triggered avalanches on steeper slopes.

Snowpack Summary

Stormy weather continues to build storm slabs and wind slabs throughout the region. Sunday's storm brought another 15-25 cm of snow, which brings the total of 40-70 cm of new snow since Tuesday the 11th. The combination of new snow and forecast strong south winds is likely forming thicker and more sensitive wind deposits at higher elevations. The new snow may still need a bit more time to form a good bond with the weak surface hoar and facets that were sitting on the surface prior to the storms.Deeper in the snowpack, there are reports of several crusts including an early season crust with facets near the bottom of the snowpack.The new snow has brought alpine snow depths up to 100-150 cm and started to cover the rocks, stumps, and open creeks at lower elevations.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.